Research On Titanium-based Getter Film For Vacuum Packaging Application

Vacuum packaging plays an important role in Micro Electro Mechanical System（MEMS）packaging technology.For some devices that require high-quality environment,leaking,outgassing of materials and other reasons will cause the vacuum level inside the cavity to deteriorate,which will seriously affect the performance of the device or even cause the device to fail to work properly.In order to make the internal pressure level of the cavity meet the working requirements and maintain long-term stability,the use of a getter film is a practical solution.First of all,based on the investigation of a large number of related documents,this article has determined the choice of titanium-based non-evaporable getter as the research object.We have studied the preparation of Ti getter films by DC magnetron sputtering and found that the specific surface area of the film is an important parameter that affects the performance of the getter,and the film deposition conditions will directly affect the specific surface area of the titanium-based film.Thus,through the adjustment of the sputtering parameters of the system,the best process parameters were determined.The results show that when the sputtering pressure is 25 mtorr,the sputtering power is 400 W,the argon flow is 20 sccm,and the substrate temperature is 25℃,the film has the largest specific surface area of 37.7±2.1 m²/g.Secondly,it is noticed that the surface of the getter film is easily oxidized after exposure to air.In order to alleviate this problem,we use an Au layer on the surface of the getter as a protective layer to prevent the surface of the getter from contacting air directly,and verify the mutual diffusion of Au and Ti at high temperatures through X-ray energy spectrum analysis（EDS）experiments.The study has determined the optimal protective layer thickness through X-ray photoelectron spectroscopy analysis（XPS）testing.For 300 nm Ti film,the optimal protective layer Au thickness is 8 nm.The study also uses XPS test to analyze the activation process of the getter film.The results show that as the heating temperature increases,the surface composition of the Ti film gradually changes from Ti O₂to low-valent oxide and metal Ti.The appearance of Ti C indicates that the activation process is in progress.There is a poisoning phenomenon,and the Au/Ti film directly completes the activation process through the mutual diffusion of Au and Ti.Finally,we performed packaging tests on the samples integrated with the Au/Ti getter,and compared the effect of the getter on the residual gas composition in the MEMS cavity.The results show that the residual water vapor in the cavity occupies a large proportion,followed by nitrogen.After the getter is added,the residual gas content in the cavity is significantly reduced,the water vapor is reduced to 22.3%,and the nitrogen is reduced to13.2%.There are different degrees of reduction,verifying the adsorption effect of the getter.